Accumulated and transient exergy analyses of pneumatic systems with isochoric and isobaric compressed air storage tanks

Abstract

Low energy efficiency is one of the most significant shortcomings of industrial pneumatic systems. The isobaric air storage tank is a new concept for improving the energy efficiency of pneumatic systems. In this study, comprehensive accumulated and transient exergy analyses are conducted to provide insight into the energy‐saving mechanism of isobaric air storage tanks. The results show that the system exergy efficiency can be improved by replacing the isochoric tank with an isobaric one. There is negligible exergy destruction in both storage tanks. However, the storage tank can bring about significant influences on other components. The isobaric tank can effectively improve the exergy efficiencies of the compressor, cooler, and regulator. Besides, there is a huge potential to improve system exergy efficiency by taking advantage of the wasted exergy from the pneumatic cylinder.

A Review of Energy Overconsumption Reduction Methods in the Utilization Stage in Compressed Air Systems

“…However, there are even fewer exergetic analyses of the utilization stage. Currently, two of those presented focus on the entire CAS [38] and the other only on the utilization stage [39]. The presented exergy losses in individual elements (pneumatic line, directional control valve, actuator, muffler, and output) differ significantly.…”

“…This modification, operating at 4 bar, led to energy savings of 18% and a reduction in system pressure fluctuations by more than 2%. The exergy efficiency of the system using the isobaric tank was 52.9%, while the traditional isochoric tank achieved an exergy efficiency of 45.8% [38].…”

Technology for efficiently converting energy stored in low-pressure compressed air to ensure security of electricity supply

“…Both systems cooperate with an isochoric compressed air tank. Despite the presented research on improving the system's functioning cooperating with an isobaric tank [13], it was decided to present isochoric tanks on the diagrams because the work does not focus on the selection of the tank, the impact of which on the engine's operation is negligible.…”

“…In work [13], the compressed air tank at constant pressure is based on a variable storage volume. There was an increase in the efficiency of the system obtained from 45.8% to 52.9% after replacing the isochoric tank with an isobaric one.…”

Exergy Analysis for the Intermittent Air Supply in Pneumatic Machines

“…Much more adequate is the second law of thermodynamics and exergy analysis, which takes into account not only changes in temperature but also pressure and the irreversibility of changes. In the literature there is some static exergy analysis of the air compression and preparation stage [23][24][25][26][27]. These analyses lack an estimate of the actual consumption of compressed air, which is defined by the final devices in the utilisation stage.…”